1. Field of the Invention
The present invention relates to an interconnection, an electric device and a method for manufacturing an electric device using a carbon nanotube.
2. Description of the Related Art
In semiconductor devices, such as large-scale integrated circuits (LSIs) and the like, higher integration and miniaturization have advanced year to year, as shown by Moor's law or a semiconductor road map. Along with the advancement of semiconductor devices, interconnections having fine dimension are also required for the semiconductor devices. The interconnection material, which started with aluminum (Al), has been replaced with copper (Cu) due to the demands for increased current density along with the miniaturization. Currently, the miniaturization is advancing due to various technical innovations based on the use of Cu for the interconnection.
However, in the 32 nm half-pitch (HP) technology node, a high current density that exceeds the limit of Cu material is required. For this reason, new materials and techniques for interconnections are required to replace the interconnections that use Cu. In response to the demand for replacing Cu in the interconnects, a candidate for an interconnection technique is to replace the Cu interconnection with an interconnection structure in which a bundle of carbon nanotubes are used.
A carbon nanotube has lower resistance and higher thermal conduction, as compared with the usual metal interconnection materials. Therefore, it has been reported that the carbon nanotubes have very high resistance characteristics to current density, on the order of about 1000 times higher than a low electrical resistance metals such as Cu and the like, per the same sectional area. It is also expected that performance deterioration caused by atomic-level migration may be substantially prevented due to the structural strength of the carbon nanotube. Hence, a high current density may be achieved by forming a bundle of carbon nanotubes and by using the bundle of carbon nanotubes as the interconnection.
On the other hand, it is difficult to grow the bundle of carbon nanotubes having the high density and fine dimension that is demanded for the 32 nm HP technology node. For this reason, with a balance between dispersion and size control of a catalyst metal used for growth of the carbon nanotube, the bundle of carbon nanotubes is grown with a lower density than that of the closest packed structure. The structure of the bundle of low-density carbon nanotubes may possibly decrease the mechanical strength when used as a plug between wiring layers. Also, the interconnection resistance may be increased.
An interconnection structure has been proposed in which a mixture of metal and carbon nanotube is used as the interconnection material (refer to WO2004/051726 pamphlet). The proposed interconnection structure decreases interconnection resistance and to suppress migration of the metal. However, it is difficult to perfectly suppress the migration of the metal included in the interconnection structure. That is, as miniaturization increases the current density, it is impossible to ignore the deterioration in performance of the interconnection structure caused by the migration of the metal.
Moreover, an interconnection structure in which the structure body which has entirely metallic characteristics, such as fullerene enclosed metal, is arranged between the carbon nanotubes (refer to JP-A 2002-329723 (KOKAI)). The fullerene has a three-dimensional structure with lower thermal conduction than the carbon nanotube. For this reason, partial disconnection of the interconnection structure may easily occur due to local temperature increase so as to increase of interconnection resistance.